1. Field of the Invention
The invention relates to a sewing machine attachably and detachably mounted with an embroidery cloth feeding unit for sewing embroideries in synchronism with the upward and downward movement of a needle bar by operating a feed dog drop mechanism of the sewing machine.
2. Description of the Related Art
Conventionally, there has been reduced to practice an embroidery cloth feeding unit (referred to also as an embroidering machine) attachably and detachably mounted to and from a sewing machine bed portion such that embroideries can be sewn by an ordinary electronic control type sewing machine for household use. According to an electronic control type sewing machine of this kind, in sewing a practical seam, because the work-cloth mounted on a needle plate of the sewing machine bed portion is fed by a feed dog, the feed dog projects from an upper face of the needle plate and is thereafter lowered to a lower side of the needle plate by a so-called four feed motion. In sewing an embroidery pattern, feeding of the work-cloth is executed by moving an embroidery frame by a cloth feeding unit mounted to the bed portion and, accordingly, the feed dog is maintained in a drop state in which the feed dog is always dropped to escape to a drop position on the lower side of the needle plate by a feed dog drop mechanism.
For example, according to the "sewing machine" disclosed in JP-A-4-371189 proposed by the applicant, there is installed a cam member integrally fixed with a vertically driving cam and a cam for dropping positioned at a lower shaft thereof, there is installed a feed dog drop mechanism for switching the position of the cam member from a vertically moving position to an escape position in accordance with a pivoted position of a pivotable operating projection, the feed dog is always driven forwardly and downwardly by a horizontally driving mechanism and, in sewing a practical seam, the work-cloth is fed by the feed dog moving upwardly and downwardly by swinging a vertically driving lever which is brought into contact with the vertically driving cam. Meanwhile, in sewing an embroidery pattern mounted to a sewing machine by pushing a cloth feeding unit along a free lower arm portion, the vertically driving lever is made to correspond to the cam for dropping by the feed dog drop mechanism and the feed dog is switched to the drop position on the lower side of the needle plate.
For that purpose, the cloth feeding unit is formed with a notched opening, an upper portion of which is opened for containing a front end portion of a bed portion when the cloth feeding unit is mounted to the bed portion of the sewing machine, and is installed with a pushing piece projected upwardly in the opening from a horizontal wall portion functioning as a bottom wall of the notched opening. When the cloth feeding unit is mounted to the bed portion, the free lower arm portion of the bed portion is fitted to connect to the notched opening. At the same time, the operating projection in the bed portion is pivoted by the pushing piece by which the cam member is switched via the feed dog drop mechanism and the horizontally driving lever is made to correspond to the cam for dropping to thereby maintain the feed dog at the drop position.
In this case, according to the technology disclosed in JP-A-4-371189, when the cloth feeding unit is mounted to the bed portion, even in the case in which the cloth feeding unit can firmly be mounted to the bed portion by pushing the cloth feeding unit to a predetermined mounting position, the pushing piece on the side of the cloth feeding unit is concealed in the unit, the feed dog drop mechanism and the operating projection for operating the drop mechanism on the side of the sewing machine are also concealed in the bed portion. Accordingly, particularly for a beginner, whether the feed dog drop mechanism is operated to be able to sew embroideries cannot be confirmed by visual observation, thereby causing apprehension in the beginner.
Even in the case in which the feed dog drop mechanism is not switched to operate in a state of an operational failure in mounting, where the cloth feeding unit is not sufficiently pushed to a predetermined mounting position, the failure cannot be confirmed. Accordingly, when the beginner attempts to sew embroideries by incorrectly believing that embroideries can be sewn, in addition to movement of cloth by the embroidery frame, there is also the incorrect operation of feeding the work-cloth by the feed dog. Further, there is also the problem that, because the pushing piece in a projected shape is installed at the horizontal wall portion of the cloth feeding unit, dirt is caught by the pushing piece and accumulates there.